Description The invention relates to a device for controlling the movement of yarn between a stationary yarn package and a yarn-processing device having cyclic operation, said device including a winding drum comprising guide means, as well as yarn release means connected between said winding drum and said yarn-processing device.

The invention furthermore relates to release means to be used in said device.

A device of this kind is known from International Patent Application O-84102361. The yarn release means of said device consist of a circular plate secured to the winding drum, with spaces containing balls provided at the edge thereof. Said balls are retained within said spaces by permanent magnets. Electromagnets to be energized are positioned at some distance from the edge of said plate, said electromagnets functioning to draw out one of said balls. The result of said drawing out is that the yarn passing between said plate and said electromagnets is stopped.

A drawback of this known device is the fact that said stopping of the release cannot be controlled with sufficient precision. Another drawback is the fact that the known device exhibits reliability and wear problems. Furthermore the known device is costly.

The object of the invention is to provide a device which does not exhibit the aforesaid drav/backs. To that end a device according to the invention is characterized in that the yarn release means include a first and a second annular element, whereby said annular elements are movable relative to each other, and whereby the yarn moves between said annular elements during operation of the device. By using two annular elements it is possible to determine the amount of yarn to be released much more accurately, since the gap can be closed at any (desired)

position.

It is noted that a device for controlling the movement of yarn is known from International Patent Application WO-A- 93/25742, wherein a ring moves around the winding drum so as to release yarn.

With the device according to the invention the release of the yarn is determined between the winding drum and for example a yarn injecting device.

•One embodiment of a device according to the invention is characterized in that during operation of the device the movable annular element can be moved by means of electromagnets to be energized.

One embodiment of a device according to the invention is characterized in that said first annular element is capable of rotating movement within said second annular element.

One embodiment of a device according to the invention is characterized in that the position of the movable annular element is determined by a position sensor. One embodiment of a position sensor consists of an optical sensor, by means of which the position of the movable annular element is determined. A position sensor may also be in the form of a coil (flux measurement) .

Another embodiment of a position sensor consists of a force sensor, which force sensor may be in the form of strain gauges, by means of which it is also possible to determine the position, for example from the resultant of a number of measured forces.

One embodiment of a device according to the invention is characterized in that the device includes a control system for controlling the movement of yarn.

Hereafter the device according to the invention will be explained in more detail by way of example with reference to the Figures, in which:

Figure 1 shows a first embodiment of a device according to the invention;

Figure 2 diagrammatically shows the first and the second annular element of Figure 1;

Figure 3 shows a second embodiment of a device according to the invention; and

Figure 4 diagrammatically shows the first and the second annular element of Figure 3. Figure 1 shows a first embodiment of a device 1 according to the invention. In operation the yarn 3 being fed is wound (by means of winding arm 4) on a winding drum 5 from a first side, said winding arm in principle being driven at the required speed by means of a motor. The yarn 7 to be released is released to a weaving machine (not shown) from the second side of the winding drum via release means. The diameter of the winding drum is substantially constant.

During the time that no yarn is to be released to the weaving machine the yarn is wound on the winding drum 5 from the first side. When yarn is to be fed to the weaving machine, the yarn release means will release yarn.

In this embodiment the yarn 7 coming from the winding drum passes between a first annular element 9 and a second annular element 13, and eventually moves on to the weaving machine (not shown) as yarn 11.

The release of yarn is influenced by electromagnets 15, as a result of which the first annular element 9 moves within the second annular element 13 (see Figure 2 for a diagrammatic indication) . By placing a number of electromagnets around the second annular element, which electromagnets are energized in succession, the first annular element 9 moves within the second annular element 13 in this embodiment. As a result of this a controllable space for the yarn is obtained, which makes it possible to control the speed and the amount of yarn to be released. Since only the first annular element moves in this embodiment, the reaction that occurs when the release of yarn is stopped is much quicker and more accurate than with the systems known so far. Figure 3 shows a second embodiment of a device 1' according to the invention. Also in this device the yarn 3 is wound on a first side of the winding drum 5 and the yarn 7 is

unwound on a second side. The release means of this embodiment include a first annular element 9 ' , which element does not move in this embodiment. In this embodiment the electromagnets 15' draw the second annular element 13' towards one of the electromagnets, as a result of which the second annular element moves around the first annular element in this embodiment while releasing a predetermined amount of yarn in a controlled manner (for a diagrammatic indication refer to Figure 4) . Also in this embodiment the mass inertia is kept small by the manner in which the ring moves, so that a quick reaction to a stop command is obtained.

The location of the moving annular element can be determined by means of a position sensor, for example. The position sensor may be an optical sensor, or for example a force sensor. The force sensor may for example be in the shape of strain gauges.

It will be apparent that the device can be modified in various manners without departing from the essence of the invention. Thus the difference in diameter between the annular elements may be made adjustable in order to be able to adjust the release gap for the various types of yarn.

It will be apparent that the annular element, for example a polygonal ring or an oval ring, may be made of a rigid material or of a flexible material. The annular element may also be fitted with (additional) magnetic material.

The device may furthermore include means for preventing vibrations.

Furthermore it is possible to direct the respective annular element to a predetermined position by means of a measurement and control system (the so-called setpoint control) , which position corresponds with the desired/required yarn feed characteristic.

In principle the movable annular element does not require axial support, as a result of which the annular element moves in a free-flying manner.

In order to ensure that the movable annular element runs

true, one embodiment may comprise means to effect this,